I've seen that, in the latest version (3.0.1), the Mod Menu API, that was deprecated, has been removed and that now mods must use com.terraformersmc.modmenu.api.ModMenuApi, but either there was an overlook or I'm getting something wrong (which is most likely), because there is no such an adress in the maven page as "./modmenu/api/ModMenuApi".
Do I have to get the api from somewhere else or is the API no longer being supported?

Ok my bad, I found out. For anyone that is a Fabric Modder and is working with ModMenu integration for the ClothConfig API, or for any other use in modding or API integration really, here is how to get the Mod Menu API:

In the build.gradle file:
repositories { [...] maven {url "https://maven.terraformersmc.com/"} }
dependencies{ [...] modImplementation "com.terraformersmc:modmenu:3.0.1" }

(Replace 3.0.1 with the version you are going to use.)